Buy icing. You can choose vanilla, strawberry, or chocolate depending on the flavor you would like your frosting to have, but keep in mind that if you use a light color and don't add cocoa, the amount of dye you need to use could alter the flavor.

Buy black food dye. You can use either the gel colorings or the liquid colorings. I prefer to use the gels because you do not need to use as much and thus the flavor is not as affected. Additionally, it can be easier to ruin the texture of the frosting with a liquid coloring.

Open your icing and put it in a large bowl, slowly add your black coloring, and stir. If you are using the gel coloring, you will not need very much, about a half ounce per cup. Keep in mind that you will need the most dye in white frosting, the second most in strawberry frosting, and the least in chocolate frosting. Note: You can also start with white butter cream frosting and add cocoa. If you do so, add about a quarter cup of cocoa per cup of frosting.

Let your frosting sit. Initially, the frosting might be a dark grey, but it will darken with time (usually an hour or so). For the best results, let the frosting sit in the refrigerator (leaving it in the light can cause the black color to fade a little).

Please be as detailed as possible in your explanation. Don't worry about formatting! We'll take care of it.
For example:Don't say: Eat more fats.Do say: Add fats with some nutritional value to the foods you already eat. Try olive oil, butter, avocado, and mayonnaise.

Tips

In a pinch, you can combine multiple colors of dye that you have on hand to create a dark frosting. Red, green, and blue work best together. This might come out more as a dark purple or a very dark grey, but it is a possibility if you don't have access to any black dye. Keep in mind that this frosting will darken with time, so let it set in the refrigerator for an hour or two after you've made it.

Chocolate icing works well to counteract the bitter taste of the dye.

You could use spray colors, but they have a minty extract to them, take heed!

Use an apron to avoid dye stains.

Black dye can stain so make sure you are well covered and use glass or stainless bowls - plastic stains.

Warnings

Do not eat the icing if it looks, feels, tastes, or smells funny.

Black dye will stain plastic mixing bowls, but glass or stainless bowls will be fine.